The invention relates to a cutter block for wood chipping machines, comprising blades mounted in blade holders, which blade holders being fastened to holding ledges by means of a tongue and groove connection while the holding ledges are mounted in a groove of a cutter block body by means of fastening screws.
A cutter block of this kind is known from Austrian Pat. No. 240,032. The holding ledge can be adjusted by means of the fastening screws for the purpose of adjusting the projection of the blade cutting edge. Because of the play inherent in this construction between the fastening screws and the holding ledges, and between the fastening screws and the cutter block body, respectively, an exact adjustment of the blade cutting edges to the desired path is possible only if these parts are produced with the utmost accuracy. A further disadvantage of this cutter block is that the blades are mounted on the blade holder only by means of an easily shifted friction-engagement connection, which may cause further inaccuracies of the projection of the blade cutting edge.
In German Offenlegungsschrift No. 2,220,003 a cutter block construction is disclosed in which shim ledges, to which the blades are positively mounted, are themselves mounted to the blade holders by means of a friction-engagement connection and the blade holders are each positively fastened to a holding ledge. With this construction the holding ledges are not adjustable relative to the cutter block body. Adjustment of the projection of the blade cutting edge is effected by adjustment screws provided on the blade carriers and supporting the shim ledges. Adjustment of the blade cutting edge projection exactly to a predetermined extent is possible with this construction, but requires a lot of work.
It is further known to fasten disposable blades in a blade holder composed of a blade carrier and a wear ledge, by means of a tongue and groove connection (German Offenlegungsschrift No. 2,514,548). The blade holders, which are also positively inserted in the cutter block in this case, are fixed in their position, so that adjustment of different blade cutting edge projections is possible only by special blade adjusting means. In order that, in the known cutter block, all disposable blades can be positioned exactly on the same path, an extremely accurate production of the cutter block and the blade holders is required, i.e. within small tolerances.
Attempts have also been made to make blade cutting edge projections adjustable by providing each blade carrier with several feather key grooves differing in their radial position relative to the cutter block, into which feather key grooves the feather keys holding the disposable blades are inserted according to the desired blade cutting edge projection. The production of such blade carriers is time consuming due to the plurality of the feather key grooves to be provided and the small tolerances with which they must be produced, and so is an adjustment of the blades.